Homogenisers



April l, 1969 M. G. STANTON HOMOGENISERS Sheet Filed Aug. l1, 1966 Nv mwmw mw s,

IA/vEA/roa MTIN GIQHY STHIVTON ,Mafia/ze/w# H nTroRNe-Ys April 1, 1969M. G. STANTON 3,436,030

HOMOGENISERS Filed Aug. 11. 196e sheet 3. of s ZWVEIVTUR mnszrm @my{Tnuwu gli?, ma +iva@ TTONEYS April l, 1969 M. G. STANTON HOMOGENISERSSheet Filed Aug. ll, 1966 M .mi

u .IJ N umm NN\ NQ Q QM, m. mlllT IW HIIIIIIII. U U. IIIIII. umm? u @bmm, mu, QN, mm wh Qh mm l @bil l l l wv@ Q mN 4 l mw uw.' .mwllmh WW umwx MN am b Q m mm .w w h. Illmwlllll nlmmll uw Q@ m. fsm fl. -11 mm A @RLQ Qn @n mh Nm, Nm,

nted States Patent O U.S. Cl. 241--199 9 Claims ABSTRACT OF THEDISCLOSURE A homogeniser has a mortar bore containing a pestle and meansfor adjusting the clearance between the pestle yand the :bore and forkeeping the pestle axially aligned in the bore. A plunger is used tomove material in the bore into contact with the pestle.

The present invention concerns homogenisers, and has particular,although not exclusive, application to tissue homogenisers.

Tissue homogenisers are used for breaking organic tissue into itselementary parts, and find much application in :tields such as the studyof the microstructure of living cells.

Tissue homogenisers have already been proposed which comprise a pestleusually having a bulbous cylindrical portion at one end and a shaft atthe other end which is connected to a motor to rotate the pestle. Thebulbous cylindrical portion is concentrically received with a smallclearance in a circular bore in a mortar. Usually the axis of the pestleand mortar is vertical. In use, the tissue to be homogenised (thehomogenant) is placed in the bottom of the mortar at the end of the boreand covered with a dispersive medium, which may conveniently be abuffered sucrose solution. The pestle is rotated and introduced into themortar, and moved towards the tissue until the tissue is trapped betweenthe bottom of the pestle and the bottom of the pestle and the bottom ofthe mortar. The shear forces in the tissue, occasioned by the contact ofthe tissue on the one hand with the rotating pestle and on the otherhand with the stationary mortar, disrupt the inter-cellular structure ofthe tissue so that the cells or groups of cells are dispersed into thedispersive medium. The dispersive medium carries the dispersed cellsinto the small clearance between the bulbous portion of the pestle andthe walls of the bore of the mortar where the shear stresses can besuiiiciently high to disrupt the cell structure itself and to dispersethe constituent parts of the cells in the dispersive medium.

In order that the tissue may be relatively uniformly homogensied in thedispersive medium, it is initially subjected to a period ofinter-cellular disruption between the end of the pestle and the bottomof the mortar in the manner previously described, following which, themortar is moved up and down relative to the pestle so that the disruptedtissue suspended in the dispersive medium is forced through theclearance between the bulbous portion of the pestle and the walls deningthe bore of the mortar.

While it is obviously a simple matter to regulate the rotational speedof the pestle relative to the mortar, in homogenisers of these knowntypes, the minimum clearance between the pestle and the mortar cannot beaccurately xed. This is because, among other reasons, the pestle issupported only in the bearings of the driving motor, and any play inthese bearings, due to wear for example, is reected in a possiblelateral movement of the bulbous-cylindrical portion which is greater inproportion 'ice to the distance of the bulbous portion from the motorbearings. Furthermore, the unsupported length of the pestle from thesebearings to the distal end of the bulbous portion has tended to be sogreat that a disadvantageous amount of flexing of the pestle can takeplace.

Recent examinations of tissue fractionation techniques have revealedthat homogenisers `of know types disrupt a large proportion of theintra-cellular particle, irrespective of their size. The largerparticles such as mitochondria and lysosomes are particularlytroublesome due to their lability. It is of particular importancetherefore that the clearance between the pestle and the mortar should beheld constant. Preferably also this clearance should be adjustable sincedifferent tissues and different classes of particles within each tissuehave different optimum homogenising conditions. The said priorconstructions do not meet these requirements fully, since even afteraccurate assembly of the motor, pestle and mortar, a tough materialoriginating in the tissue, such as collagen, momentarily passing throughthe clearance at one point between the pestle and mortar, can causeexing of the pestle and movement in the motor bearings which will leadto very high shear stresses in the dispersive medium at a diametricallyopposite point of the clearance due to a reduction in the localmagnitude of the clearance.

The present invention seeks to overcome at least some of the problemsencountered with the `known homogenisers, and according to one aspect ofthe present invention, there is provided a homogeniser comprising amortar assembly having walls detining a bore of circular transversecross-section, a pestle assembly having at least a portion which is ofcircular transverse cross-section and which is concentrically receivedin the bore at a selected axial disposition relative to the bore with anannular clearance, in normal operation, between the said portion of thepestle assembly and the walls of the bore, at least two axially spacedbearings each located between the pestle assembly and the mortarassembly and arranged to permit relative rotation therebetween, couplingmeans which can be coupled to driving means for rotating the pestleassembly relative to the mortar assembly and guiding means for directinghomogenant material towards the annular clearance between the saidportionV of the pestle assembly and the walls deiining the bore.

According to another aspect of this invention, there is provided ahomogeniser comprising a mortar assembly having walls defining a bore ofcircular transverse crosssection, a pestle assembly having at least aportion of circular transverse in cross-section concentrically receivedin the bore at a selected axial disposition relative to the mortarassembly, with an annular clearance in normal operation, between thesaid portion of the pestle assembly and the walls of the bore, bearingmeans permitting relative rotation of the pestle assembly and the mortarassembly, the mortar assembly having constraining means serving todistribute loads on the pestle assembly substantially uniformly aroundthe circumference of the said walls whereby to maintain theconcentricity of the pestle assembly and the bore.

Preferably, the said bearing means comprises at least one thrust bearingwhich, in operation, is engaged in an axis direction, by the pestleassembly, the constraining means comprising a casing means serving toengage the said thrust bearing in an opposite axial direction, thecasing means surrounding at least a part of the pestle assembly and atleast part of the walls defining the bore and engaging the said walls incircumferential and axial directions.

The bearings serve to maintain substantially accurate alignment betweenthe mortar assembly and the pestle, whilst allowing relative rotationtherebetween.

At least one of the bores and the said portion of the pestle assemblymay be tapered so that the area of the annular clearance between thesaid portion of the pestle assembly and the walls of the bore varies asbetween axially spaced transverse cross-sections through the said bore.This enables the homogenant material to be subjected to varying shearstresses, in operation ofthe homogeniser, as it passes through theannular clearance.

Both the bore and the said portion of the pestle assembly may be taperedin the same axial direction, and the angles of taper of the said portionand the bore may be substantially equal so that the radial clearancebetween the said portion and the walls of the bore is substantiallyuniform.

The said portion of the pestle assembly and the mortar assembly may beaxially movable relative to each other so that the magnitude of theannular clearance may be varied.

Preferably at least one of the said bearings is a thrust bearing wherebyaxial loads on the pestle are resisted by the mortar assembly.

The guiding means may comprise a conduit in the mortar assembly formingan extension of the said bore, and there may be provided a plunger orlike means movably disposed in the said conduit whereby any homogenantmaterial in the conduit can be moved and directed towards the saidannular clearance. There may be means for moving the plunger or likemeans relative to the said portion of the pestle assembly.

The tip of the said portion of the pestle assembly and the face `of theplunger or like means nearest to the tip may be so formed as to berotatably cooperable whereby the homogeniser may be operated withhomogenant material pressed between the tip of the said portion of thepestle assembly and the said face of the plunger or like means.

At least part of the said portion of the pestle assembly may be rifledso as to enhance, in operation, the shearing of homogenant in the saidannular clearance.

The mortar assembly may be formed with at least one port on each axialside of the said portion of the pestle assembly respectively for theentrance of homogenant material to the annular clearance and for theexit of homogenate material therefrom.

Preferably, the previously mentioned riing of the said portion of thepestle assembly is such as to assist, in operation, the flow of materialfrom the entrance port to the exit port.

There may be provided a jacketing wall surrounding, and spaced from, thesaid walls of the bore so as to dene a space outwardly of the bore forreceiving a temperature regulating uid, such as water.

At least one of the said bearings may be adjustable for wear `or playwhereby the said portion of the pestle assembly may be maintainedsubstantially concentric with the walls of the bore.

'Embodiments of the invention will now be described by way of exampleonly and with reference to the accompanying drawings in which:

FIGURE 1 is a diagrammatic cross-section of one form of tissuehomogeniser in accordance with the invention,

FIGURE 2 is a partly-sectioned perspective view of part of a needleroller bearing employed in the homogeniser of FIGURE l, and

FIGURE 3 is a diagrammatic cross-section of another form of tissuehomogeniser in accordance with the invention.

In the drawings, any item which appears in more than one of the figuresis given the same reference numeral in each igure.

In the FIGURE 1, the tissue homogeniser, generally indicated byreference numeral 10, comprises a mortar assembly including a mortartube 11 having an internal bore 12 of circular transverse cross-section,and a pestle assembly comprising a pestle 13 of circular transversecross-section, a portion 14 of which is concentrically received in thebore 12.

The mortar tube 11 is received as a low-tolerance sliding t in twoaxially spaced internal annular flanges 15, 16 of an outer casing 17,forming part of the mortar assembly, the outer casing 17 surrounding themortar tube 11 and being spaced therefrom to dene an annular space 1Swhich, in operation, is supplied with water at a selected temperature,to regulate the temperature in the bore 12 of the mortar tube 11. Theinternal flanges 15, 16 are each recessed on their inner faces, andrubber O-rings 19, 20 are received in the recesses to prevent the escapeof water from the space 18. The outer casing 17 is provided with inletand outlet ports 21, 22 for the water.

To the right (as viewed in FIGURE 1) of the O-ring 20 in ange 16, themortar tube 11 has a feed port 23 which registers with a port 24 in theouter casing 17, and to the right of the ports 23, 24, the outer casing17 is provided with an internal shoulder 25 which cooperates with anexternal shoulder 26 on the mortar tube 11 with a rubber 'O-ring 27therebetween to prevent any leakage of homogenant fed from the ports 23,24 between the outer surface of the mortar tube 11 and the inner surfaceAof the outer casing 17.

The external shoulder 26 of the mortar tube 11 is provided with finepitch external threads 2S which coopearte with tine pitch internalthreads of the outer casing 17 so that the mortar tube 11 can be screwedinto position in the outer casing 17. The right-hand end (as viewed inFIGURE 1) of the mortar tube 11 is formed with a ilange 29 which engagesagainst the face 30 of the outer casing 17 with a spring washer 31therebetween so that the relative axis positions of the mortar tube 11and the outer casing 17 are accurately defined.

The other, left-hand, end of the outer casing 17 has a widened portion17a which accommodates a driving pulley wheel 32 secured on the pestle13 by means of a radial grub-screw 33, and is provided with internalthreads 34 which cooperate with external threads of an end-cap 35 whichcloses the left-hand end of the homogeniser 10. The widened portion 17ahas two peripherally-spaced axially-extending slots 36 (only one ofwhich is visible in FIGURE 1) extending from the end-cap 35 so that anendless driving belt 37 can pass from the driving pulley wheel 32 to adriving motor (not shown).

The pestle 13 and pulley ywheel 32 are mounted for rotation relative tothe outer casing 17 and the end-cap 35 by means of two axially spacedbearings generally indicated by 37a and 37b respectively.

The left-hand bearing 37a is a spring-loaded journal and thrust bearingwhich comprises an inner race 38 trapped between a shoulder 39 on thepestle 13 and a Washer 40 which is threada'bly attached on the pestle13, and an outer race 41 in the form of an annular ring which isslidably received in the end cap 35, there being a number 'of ballbearings 42 which axially and radially separate the iner race 38 and theouter race 41. The outer race 41 is urged axially towards the inner race38 by a compression spring 43 which is retained by a washer 44 securedto the end cap 35. The axial position of the pestle 11 and the bearing37a relative to the outer casing 17 and the end cap 35 is determined bythe axial position of an adjusting screw 45 which is threadably receivedin the end cap 35 and which acts on the pestle 13 in opposition to thecompression spring 43 through a trapped ball bearing 46.

It will be apperciated that any axial thrust towards the left, in FIGUREl, on the pestle 13, will cause the shoulder 39 to engage with the innerrace 38 of the thrust thrust bearing 37a the spring 43 then distributingthe axial load via the Washer 44 substantially uniform in acircumferential sense around the face of the end cap 35. The uniformlydistributed load is then transmitted to the mortar tube 11 by theengagement of the outer casing 17 with the end cap 35 on the one handand the mortar tube 11 on the other hand. The flanges 1S, 16 and thecooperating threads 28 between the outer casing 17 and the mortar tube11 constrain the mortar tube 11 and maintain the concentricity of thepestle 13 and mortar tube by distributing any axial loads on the pestle13 substantially uniformly around the circumference of the mortar tube11.

The right-hand bearing 37b (as viewed in FIGURE 1) is a needle rollerbearing of the type which is adjustable for radial clearance, andcomprises, as will be seen from FIGURES l and 2, an annular inner race47 which is retained between a shoulder 4S on the pestle 13 and a springclip 49, and a number of needle rollers 50r disposed in a suitableretaining cage for rolling around the radially outer face of the innerrace 47 and the radially inner face of an outer race 52. The needlerollers 50v in their retaining cage can move axially with respect to theinner race 47 but are prevented from such movement relative to the outerrace 52 by the annular anges 53, thereon (see FIGURE 2). The outer race52 is trapped between an internal shoulder 54 of the outer casing 17 anda threadably attached internal collar 55 on the outer casing 17. Theouter race 52 is corrugated in axial crosssection so that by varying theaxial spacing of the internal collar 55 and the internal shoulder 54,the radial distance between the outer race 52 and the inner race 47 canbe varied to take up any wear in the needle rollers 50.

Between the bearing 37b and the adjacent end of the mortar tube 11 areprovided two oppositely facing conventional rotary seals 56 which areaxially urged apart into cooperation with internal shoulders 50 on theouter casing 17 by an annular spring 57. The upper side of the outercasing between the seals 56 is provided with a grease nipple 59 closedby a spring-urged ball valve 60. The lower side of the outer casing 17between the seals 56 is provided with a grease drainage hole closed by aremovable threaded plug 61. In operation, the space between the tworotary seals 56 is packed with a biologically inert grease to avoid thepossibility that material in the mortar tube 11 could pass to thebearings 37b, 37a and contaminate and damage them. The outer casing 17is provided with a discharge port 62 between the right-hand seal 56 andthe adjacent end of the mortar tube 11 so that material to behomogenised (the homogenant) can be fed continuously to the feed port 23and discharged continuously from the discharge port 62.

During operation of the homogeniser 10, the homogenant passes from thefeed port 23 through the bore 12 in the mortar tube and via the annularclearance 63 between the right-hand portion 14 of the pestle 13 and thesurrounding wall of the mortar tube 15 and is discharged at thedischarge port 62. While the homogenant passes through the clearance 63,it is subject to shear forces caused by the rotation of the portion 14of the pestle relative to the surrounding wall of the mortar tube 11which disrupt the tissue to a degree dependent on the width of theclearance `63 and on the speed of rotation of the pestle 13. Theprovision of the two axially spaced bearings 37rz, 37b and therelatively short and thick pestle 13 ensures that the pestle 13 will notbe ilexed or bent by the passage of hard tissue materials such ascollagens, through the clearance 63, so that the clearance 63 will bemaintained substantially uniform, in operation, in each transversecross-section therethrough.

It will be seen that the portion 14 of the pestle 13 within the mortartube 11 is tapered away from the end cap 35, and that the surroundingwall of the mortar tube 11 is substantially parallel, in axialcross-section, to the portion 14 so to provide a bore which taperstowards the feed port 23 at substantially the same angle as the portion14 of the pestle 13. Accordingly, the clearance 63 will be substantiallyuniform at all regions between the portion 14 and the mortar 11,although the difference in the areas and the mean radii of the axiallyopposite ends of the clearance 63 will provide that the shear stressesset up in the homogenant will be smallest towards the tip 13a ot thepestle 13 and will increase as the homogenant passes through theclearance 63 towards the discharge port 62.

It will be appreciated that if the axial position of the pestle 13 isadjusted relative to the mortar 11, by means of the adjusting screw 45,the magnitude of the clearance can be regulated. Thus, if the adjustingscrew 45 is so turned that the pestle 13 is moved to the right, inFIGURE l, relative to the mortar tube 11, the clearance `63 will bereduced. Similar, if the adjusting screw 45 is so turned that the pestle13 is moved to the left, (by the action of the spring 43) clearance 6-3will be increased. Since the shear stresses which disrupt homogenant inthe clearance 63 depend on the magnitude ofthe clearance, as well as therelative rotary speeds of the portion 1-4 of the pestle 13 and themortar tube 11, it is possible to arrive at a selected degree ofdisruption of homogenant by twining the adjusting screw 45, and theremay be no need to change the speed of rotation of the pestle 13 duringoperation.

The homogeniser 10 is further provided with a plunger 64 (partlysectioned in FIGURE 1) which is movably disposed in the parallel-sidedportion 12a of bore 12 for propelling homogenant, if necessary, towardsthe pestle 13 from the feed ports 23, 24. The plunger 64 is moved inbore 12 by means of a guide rod `65 passing through the ange 29 andactuated by electric or mechanical means (eg. clockwork), or by hand.

The guide rod 65 is formed with a key-way 66, and a peg 67 housed in anaperture in the right hand end of the mortar tube 11 engages in thekey-way 66 to the plunger 64 against rotation about its axis.Alternatively the guide rod 65 and its hole in the flange r29 may be ofnon-circular cross-section.

The propelling face 68 of the plunger 64 has a complementary shape tothe tip 13a of the pestle 13 so that the plunger 64 and the pestle 13can cooperate whilst there is relative motion therebetween. In thisinstance, the tip 13a is of conical form and the propelling face 68 isof internally coned form so that any homogenant trapped between theplunger 64 and the pestle 13 will be subjected to shearing forces over agreater area than would be the case were the pestle tip 13a and thepropelling surface 68 at.

To operate the tissue homogeniser 10 the homogenant is passed into theparallel sided portion 12a of the bore 12 in the mortar tube 11 throughthe ports 23, 24. If the homogenant is initially a solid piece oftissue, it is Iirst sliced into suitably small pieces, and a suitabledispersive medium, such as buffered sucrose solution, is also passedinto the portion 12a of the bore 12. The motor (not shown) driving thebelt 37 is now started, and the plunger 64 advanced towards the tip 13aof the rotating pestle 13. The shear stresses occasioned in the tissueby contact on the one hand with the rotating pestle 13 and on the otherhand with the non rotating plunger 64 disrupts the intercellularstructure of the tissue so that cells and groups of cells becomesuspended in the dispersive medium. The dispersive medium carries thesuspended cells through the annular clearance 63, where the shearstresses, which can be selected by turning the adjusting screw 45 and/or by choosing an appropriate rotational speed of the pestle 13, disruptthe cells to the required extent. The homogenate leaving the homogeniser10 at the exit port 62 can be recirculated through the homogeniser 10`via the feed ports 24, 23 to achieve further disruption of the tissue,if required.

For homogenants which comprise low viscosity material, such as thepreviously mentioned buffered sucrose solution, the homogeniser 10 mayconveniently be arranged for loading with the axis vertical and theflange 29 lowermost, the low viscosity component of the homogenant beingpassed into the portion 12a of the bore 12 from a syringe (not shown)having a discharge nipple which can be sealingly received in port 24.The operation of the syringe will initially ll or partly ll the bore 12.

As tissue normally sinks in a buttered sucrose solution it is necessaryto propel the tissue through the annular clearance 63 between theportion 14 of the pestle 13 and the surrounding tapering wall of themortar tube 11 by advancing the plunger 64 towards the tip 13a of thepestle 13.

In a practical example of the homogeniser 10, the pestle 13 and mortartube 11 are formed from stainless steel, whilst the outer casing 17 isof the aluminium based alloy, Dural. The cantilevered length of thepestle 13, i.e. to the right of the bearing 37b is 21/2 inches, theuntapered diameter of the pestle about 3%: inch and the angle of taperof the pestle 13, relative to its axis of rotation, about 5 degrees.

For routine cleaning, the outer casing 17 is formed in two axiallydiscrete portions which are separable in the plane of the mating faces69 of external ilanges 70 formed on the portions of the outer casing 17.The flanges 70 are clamped to each other by bolts 71 with a gasket 72(or rubber O-ring) accommodated therebetween to prevent the escape ofwater from the annular space 18. When the bolts 71 have been undone, andthe two portions of the outer casing 17 axially separated, the mortartube 11 is removed with the right-hand portion (as viewed in FIGURE l)of the outer casing 17 leaving the portion 14 of the pestle 13protruding from the left-hand portion of the outer casing 17 andavailable for cleaning. The mortar tube 11 can be cleaned either Whilstin situ in the right-hand portion of the outer casing 17 or afterremoval therefrom by unscrewing the threads 28 adjacent the ange 29 ofthe mortar tube 11.

The tissue homogeniser can ibe dismantled for more thorough servicing oroverhaul by unscrewing the end cap 35 from the outer casing 17 (by meansof threads 34), after which the end cap 35, the bearings 37a, the pestle13, the pulley wheel 32 and the inner race 47 ofthe bearings 37b can bewithdrawn to the left as seen in FIG. 1.

The tissue homogeniser 110 shown in FIGURE 3 is generally of similarconstruction to the tissue homogeniser depicted in FIGURE 1, and thedifference between these designs will be highlighted below:

The tip 13a of the pestle 13 is rounded rather than conical, and isprovided with spiral grooves 75 similar to the rilling of a gun andhaving a small angle of twist. The grooves 75 extend about a third ofthe length of the portion 14 of the pestle 13, from the tip 13a, and ithas been found that they assist the separation of cellular tissue frommore coherent materials such as collagens and also enhance the ow ofhomogenant through the homogeniser 110 in the Same manner as anArchimedian screw, provided the direction of twist is appropriatelychosen to suit the direction of rotation of the pestle 13. Thepropelling face 68 of the plunger 64 is internally rounded to the sameinternal shape as the external shape of the tip 13a of the pestle 13 soas to be complementary in shape thereto and to permit rotationalcooperation therewith.

IIn this embodiment, the mortar tube 11 has an external tapered surface111 at its left-hand end (as viewed in FIGURE 3) which cooperates withan internal tapered surface 121 forming the radially inner face of thelefthand flange 21. At the right-hand end of the mortar tube 11, thethreads 28 have been omitted, and the ilange 29 is urged towards theouter casing 17 yby bolts 77 which engage in threaded lblind bores 78 inthe outer casing 17. The cooperation of the tapered surfaces 111, 121 ofthe mortar tube 11 and the outer casing 17 together with the provisionof the bolts 77 to provide engagement between the mortar tube 11 and thecasing 17 enables the pestle 13 and the mortar tube 11 to jbe accuratelyaligned after each disassembly. Preferably, when the homogeniser 110 isassembled, there is a small gap 80 between the adjacent faces of theouter casing 18 and the flange 29 to allow for compensation for any wearwhich may have taken place in the tapert surfaces 111, 121 by adjustmentof the bolts 77. In a variant of this embodiment, the ange 29 isextended transversely (as shown 4by dotted lines 29a) and the externalflanges 70 and flange 29a are connected by bolts 77a (shown dotted) soas to increase the rigidity of the mortar assembly.

The mortar tube 11 is further provided with an external shoulder 79 tothe left (as viewed in FIGURE 3) of the shoulder 26. The shoulder 79cooperates with a shoulder 81 to trap the rubber O-ring 20 therebetween(instead of disposing the O-ring 20 in a groove in the internal flange16 asin the ligure/embodiment), the O- ring 20 serving to preventseepage of water outwardly from the annular space 18. The tissuehomogeniser also employs an O-ring 172 located in cooperating grooves inthe flanges 70 instead of the gasket 72 employed in the homogeniser 10of FIGURE 1.

It will Abe seen in both of the described embodiments that since themean radius of the annular clearance 63 between the portion 14 of thepestle 13 and the surrounding internally tapered surface of the mortartube is smallest nearest to the feed port 23 and largest nearest to thedischarge port 62, the homogenant is initially subjected to the lowestshear stresses, and as it progresses through the annular clearance 63towards the exit port 62 the shear stresses become greater. It may fromtime to time be preferable that the shear stresses suffered by thehornogenant are initially greater than they are just before thehomogenant reaches the exit port. Accordingly, it is contemplated thatthe homogenant may be loaded into the homogeniser 10 or 110 via thedischarge port 62, to issue as homogenate vvia the feed ports 23, 24.Alternatively, the homogeniser 10 or 110` may be so adapted that thetapering portion 14 of the pestle 13 and the sur rounding internallytapered surface of the mortar tube 11 taper the opposite way to thatshown in FIGS. 1 and 3, so that the annular clearance 163 between thesesurfaces decreases in mean radius in passing from the ports 23, 24 tothe discharge port 62 of the homogeniser 10 (or 110). In thisalternative, the homogeniser would need to be assembled in a mannerdilering from the manner shown in FIGS. 1 and 3: for example, the`pestle 13 could be formed with the tapering portion threadably attachedto the remainder of the pestle 13 from opposite axial ends of thehomogeniser.

It is contemplated that instead of both the pestle 13 and the internalbore of the mortor tube 11 having tapered surfaces or portions, only thepestle 13 or the bore 4may have a tapered surface or portion.Furthermore, whilst in the described embodiments, the angles of taper ofthe portion 14 of the pestle 13 and the internally tapered surface ofthe mortar tube 11 are substantially equal, the angles of taper of thepestle 13 and the mortar tube 11 may diler to provide a requireddisrupture effect ofthe material to be hornogenised.

Various combinations of features of the described embodiment may beemployed without departing from the invention.

I claim:

1. A homogeniser comprising a mortar assembly having walls defining abore of circular transverse crosssection, a pestle assembly having atleast a portion of circular transverse cross-section concentricallymounted in said bore at a selected axial disposition relative to themortar assembly, said portion and said walls normally defining an`annular clearance, said mort-ar assembly delining a conduitcommunicating with said annular cleavance, plunger means movablydisposed in said conduit for urging homogenant material in said conduittowards said annual clearance, and the pestle assembly and the plungermeans having cooperating opposed faces adopted to permit rotation of thepestle assembly relative to the plunger means.

2. A homogeniser -as in claim 1, wherein said bore defined by said wallsof said mortar assembly land said conduit are contigous and have theiraxes aligned.

3. A homogeniser as in claim 2, wherein said cooperating opposed facescomprise an end face of said pestle assembly and an end face of saidplunger means.

4. A homogeniser as in claim 3, wherein the end face of the pestle is ofgeneral conical form.

5. A homogeniser as in claim 3, wherein the end face of the pestle isrounded.

6. A homogeniser comprising a mortar assembly having walls dening a boreof circular transverse crosssection, a pestle assembly having at least aportion of circular transverse cross-section concentrically mounted inthe -bore at a selected axial disposition relative to the mortarassembly, said portion and said walls normally defining an annularclearance, and two spaced apart bearing means supporting said pestleassembly for rotation relative to said mortar assembly, one of saidbearing -means being adjustable for wear whereby the said portion of thepestle assembly may be maintained substantially concentric with thewalls of the bore.

7. A homogeniser 4as in claim 6, wherein said adjustable bearing meansis nearer said portion of said pestle assembly than the other bearingmeans.

References Cited UNITED STATES PATENTS 1,985,569 12/1934 Haskell et al.241-247 1,988,743 1/ 1935 MacKenzie 241-247 X 2,173,975 9/1939 Lyons241-256 X 2,231,421 2/1941 Gitzendanner 241-256 2,338,198 1/1944 Pall241-199 X 2,547,330 4/1951 Morden 241-247 X ANDREW R. JUHASZ, PrimaryExaminer.

F. T. YOST, Assistant Examiner.

U.S. C1. X.R. 241-247, 256

